Si la cisterna vuelve a hacer ruido por la noche, llamaré a la fontanera mañana.

In this sentence, la cisterna most naturally means the toilet tank / toilet cistern in a bathroom.

A native English speaker might first think of a big water tank, and cisterna can mean that in other contexts, but in everyday home-repair Spanish, la cisterna often refers to the part of the toilet that fills with water and flushes.

So here, the idea is probably that the toilet tank is making noise at night.

Volver a + infinitive is a very common Spanish structure meaning to do something again.

So:

• vuelve a hacer ruido = it makes noise again / it starts making noise again
• literally: it returns to make noise

Examples:

• Ha vuelto a llover. = It has rained again.
• Vuelvo a intentarlo. = I’m trying again.

So in your sentence, la cisterna vuelve a hacer ruido means the noise is not new; it is happening again.

Because hacer ruido is the standard Spanish expression for to make noise.

• hacer = to make/do
• ruido = noise

So:

• hacer ruido = to make noise

This is much more natural than trying to translate English word-for-word in some other way.

You may also hear other verbs depending on the situation:

• sonar = to sound / to ring
• meter ruido = to make noise, but more colloquial and often more like to be noisy
• hacer un ruido raro = to make a strange noise

Here, hacer ruido is the most normal neutral choice.

In Spain, por la noche is the usual way to say at night.

Common time expressions are:

• por la mañana = in the morning
• por la tarde = in the afternoon / evening
• por la noche = at night

So:

• hace ruido por la noche = it makes noise at night

En la noche does exist, but it is less common in Spain in this kind of sentence and can sound more literary, regional, or context-specific. For a learner of Spanish from Spain, por la noche is the safer and more natural option.

Because this is a real, possible future condition, and in Spanish that pattern is:

• si + present indicative, then
• future (or another suitable main verb)

So:

• Si la cisterna vuelve a hacer ruido..., llamaré...
• If the toilet tank makes noise again..., I’ll call...

This is one of the most important patterns to remember:

• Si tengo tiempo, iré. = If I have time, I’ll go.
• Si llueve, nos quedaremos en casa. = If it rains, we’ll stay home.

English learners often expect a subjunctive because the situation is future, but after si in this kind of sentence, Spanish normally uses the present indicative, not the present subjunctive.

No. That would be incorrect here.

After si for a real future condition, Spanish uses the present indicative:

• correct: Si la cisterna vuelve a hacer ruido...
• incorrect here: Si la cisterna vuelva a hacer ruido...

The form vuelva is subjunctive, but that is not used in this type of si clause.

A useful rule:

• si + present indicative for likely/real conditions
• si + imperfect subjunctive for unlikely/hypothetical conditions

For example:

• Si la cisterna volviera a hacer ruido, llamaría a la fontanera. = If the toilet tank were to make noise again, I would call the plumber.

Because the speaker is talking about a future action: I will call tomorrow.

Llamaré is the 1st person singular future of llamar:

• llamaré = I will call

This matches the conditional idea:

• If X happens, I will do Y.

Spanish often uses the simple future like this:

• Si viene, hablaré con él.
• Si no funciona, compraremos otro.

You could also say:

• voy a llamar a la fontanera mañana

That would also be natural. But llamaré is perfectly standard and slightly more compact.

Because llamar a alguien means to call someone, and when the direct object is a person, Spanish uses the personal a.

So:

• llamaré a la fontanera = I’ll call the plumber

Even though la fontanera is the direct object, Spanish still uses a because it is a person.

More examples:

• Veo a María. = I see María.
• Llamamos al médico. = We call the doctor.
• Voy a invitar a mis amigos. = I’m going to invite my friends.

So the a is not optional here.

Yes. La fontanera is the feminine form, so it means the female plumber.

• el fontanero = the male plumber
• la fontanera = the female plumber

In English, plumber does not show gender, but in Spanish many profession nouns do.

Also, in Spain, fontanero / fontanera is the usual word for plumber. In many parts of Latin America, learners may hear plomero / plomera instead.

So this sentence sounds especially natural for Spain.

Yes, mañana can mean either:

• tomorrow
• morning

But the context makes the meaning clear here.

In this sentence:

• llamaré ... mañana

because llamaré means I will call, mañana clearly means tomorrow, not in the morning.

Compare:

• Llamaré mañana. = I’ll call tomorrow.
• Llamaré por la mañana. = I’ll call in the morning.

So if you specifically wanted in the morning, you would usually say por la mañana.

Because the sentence begins with the if-clause:

• Si la cisterna vuelve a hacer ruido por la noche, ...
• then the main clause:
• llamaré a la fontanera mañana.

In Spanish, as in English, it is normal to put a comma after the opening conditional clause when it comes first.

You could also reverse the order:

• Llamaré a la fontanera mañana si la cisterna vuelve a hacer ruido por la noche.

That version is also correct, and then the comma is often not needed.

Yes. Spanish word order is fairly flexible here.

These are all natural:

• Si la cisterna vuelve a hacer ruido por la noche, llamaré a la fontanera mañana.
• Mañana llamaré a la fontanera si la cisterna vuelve a hacer ruido por la noche.
• Llamaré mañana a la fontanera si la cisterna vuelve a hacer ruido por la noche.

The differences are mostly about emphasis:

• putting mañana earlier can emphasize tomorrow
• putting the si clause first emphasizes the condition

The original sentence is very natural and clear.

Yes, you could, and the meaning would be very similar.

For example:

• Si la cisterna hace ruido otra vez por la noche, llamaré a la fontanera mañana.

This means:

• If the toilet tank makes noise again at night, I’ll call the plumber tomorrow.

Both are correct:

• vuelve a hacer ruido = makes noise again / starts making noise again
• hace ruido otra vez = makes noise again

The version with volver a + infinitive is often slightly more idiomatic and compact in Spanish.

Yes, it sounds very natural for Spain, especially because of fontanera.

A few Spain-specific or Spain-typical points are:

• fontanero / fontanera for plumber
• por la noche as a standard everyday expression
• cisterna being a very normal word for the toilet tank

In Latin America, some wording might change depending on the country, especially the plumber word:

• fontanero/a in Spain
• often plomero/a in many Latin American countries

But the grammar of the sentence would still be widely understood across the Spanish-speaking world.